Laboratory Tests for Addisonian Crisis
In suspected Addisonian crisis, immediately draw blood for serum cortisol and ACTH before treatment, but never delay emergency hydrocortisone and fluid resuscitation while waiting for results. 1, 2
Essential Immediate Laboratory Tests
When Addisonian crisis is suspected, the following blood tests should be obtained stat:
Serum cortisol and ACTH - These are the definitive diagnostic tests. A basal cortisol <250 nmol/L with elevated ACTH in acute illness is diagnostic of primary adrenal insufficiency. 1 Cortisol <400 nmol/L with elevated ACTH raises strong suspicion. 1
Serum electrolytes (sodium and potassium) - Hyponatremia is present in approximately 90% of cases, while hyperkalemia occurs in only about 50% of patients, so its absence does not rule out the diagnosis. 1, 2
Creatinine and BUN - These are typically elevated due to prerenal renal failure from volume depletion. 2
Blood glucose - Hypoglycemia is common, particularly in children but less frequent in adults. 2
Serum calcium - Mild to moderate hypercalcemia occurs in 10-20% of patients. 2
Additional Diagnostic Laboratory Work
Beyond the immediate crisis workup, obtain:
Complete blood count - To assess for infection or other precipitating causes. 3
Tests for precipitating causes - Including cultures if infection is suspected, as gastrointestinal illness with vomiting/diarrhea is the most common trigger. 2, 3
Confirmatory Testing (Post-Crisis)
The cosyntropin (synacthen) stimulation test is the standard confirmatory test, but should only be performed after the patient is stabilized:
- Administer 0.25 mg cosyntropin intramuscularly or intravenously. 1
- Measure serum cortisol at baseline, 30 minutes, and/or 60 minutes. 1
- A peak cortisol value should exceed 500-550 nmol/L to be considered normal. 1
Critical Clinical Pitfalls
Treatment must never be delayed for diagnostic procedures. 4, 1, 2 If clinical suspicion exists, give intravenous hydrocortisone 100 mg immediately and start 0.9% saline infusion at 1 L over the first hour. 3 The diagnosis can always be established later, even after treatment has commenced. 4
The absence of hyperkalemia does not exclude Addisonian crisis, as it is present in only half of cases. 1, 2 Similarly, while hyponatremia is very common (90% of cases), its absence should not prevent treatment if clinical suspicion is high. 2
Etiologic Workup (After Stabilization)
Once the acute crisis is managed, determine the underlying cause:
21-hydroxylase autoantibodies (21OH-Ab) - Positive in autoimmune Addison disease, which accounts for approximately 85% of cases in Western Europe. 4
CT scan of adrenals - If 21OH-Ab negative, to evaluate for hemorrhage, tumor, tuberculosis, or other infiltrative processes. 4
Very long chain fatty acids (VLCFA) - If adrenoleukodystrophy is suspected. 4